This VCF has been heavily influenced by Jürgen Haibles SSM 2040 filter clone. I constructed it using mostly SMD parts, hence the name. The circuit differs from Jürgens, in a few details. I operate the filter core with different supplies. (+15V,+5V,0V) Thus I didn't need to lower the ground of the expo convertor. I omitted the voltage controlled resonance, because it is easy enough to get. If you have a spare VCA you can patch it if you need it. I'll maybe add it later, when I do a board revision.